Rim Joist Insulation | Closed-Cell Spray Foam | Waukesha & Milwaukee, WI

band joist spray foam, closed-cell foam Milwaukee, basement air sealing Wisconsin

Cold floors and high heating bills usually start at the rim joist. Cozy Walls seals and insulates rim joists with closed-cell spray foam across Waukesha, Milwaukee, and Southern Wisconsin.

262-592-5381

**Discounts apply to whole-home projects with a minimum job size of $5,000. One discount per household.

Rim Joist Insulation in Waukesha & Southern Wisconsin

If your floors are cold in January, your furnace runs constantly, or you feel a draft along the basement walls, the rim joist is one of the first places to look.

The rim joist — sometimes called the band joist — is the wood framing that runs around the perimeter of your house where the floor system sits on top of the foundation. It’s thin, it’s exposed to outside air on one side, and in most Wisconsin homes it was never sealed properly. Square foot for square foot, it’s one of the largest sources of heat loss and air leakage in the entire building.

Cozy Walls seals and insulates rim joists with closed-cell spray foam, which stops the air leak and the heat loss in a single application.

Why the Rim Joist Matters So Much in Wisconsin

A typical home has 150 to 250 linear feet of rim joist. In an unsealed house, that perimeter behaves like a continuous gap between your basement and the outdoors. Here’s what that costs you:

Cold floors on the first level.

Outside air enters at the rim, cools the floor framing, and you feel it through the floor above.

Stack effect.

Warm air rises and escapes through the attic, and cold air gets pulled in at the bottom of the house to replace it. The rim joist is the main entry point.

Higher heating bills.

Your furnace isn’t losing to the walls as much as you’d think — it’s losing to air movement.

Moisture problems.

Humid summer air hitting cold framing condenses. Over years, that means musty smells, mold, and rot in the band board and sill plate.

Why Fiberglass Batts Don’t Work Here

Almost every home we open up has fiberglass stuffed into the rim joist cavities. It looks like insulation. It isn’t doing the job.

Fiberglass is air-permeable. Air moves straight through it, which means it does nothing to stop the leak — and because the batt lets humid interior air reach the cold rim board, it can actually make condensation worse. Pull one out in February and you’ll often find it damp, black along the edges, or frozen to the wood.

The rim joist needs an air barrier, not just an insulator. That’s a different product.

We inspect the full rim joist perimeter, identify problem areas, remove existing fiberglass when necessary, and apply closed-cell spray foam to seal the rim board and sill plate.

What the Job Looks Like

Walkthrough and measurement

We inspect the full perimeter, note any water damage or rot, measure linear footage, and identify obstructions — ductwork, wiring, plumbing runs.

Prep

Existing fiberglass gets removed and hauled away. Surfaces are cleaned and any obvious moisture issues are flagged before we spray.

Application

Closed-cell foam is applied to the rim board and across the sill plate, sealing the joint where the framing meets the foundation. We follow Wisconsin code requirements for thermal and ignition barriers where they apply.

Cleanup and walkthrough

We clean the work area and walk the job with you before we leave. Most rim joist jobs are completed in a single day. The foam is tack-free within minutes and fully cured within hours.

Closed-Cell Spray Foam — The Right Product for Rim Joists

Cozy Walls specializes in pour-in-place injection foam for existing walls, but the rim joist is an open cavity, which calls for a different material. For this application we use closedcell spray polyurethane foam, and here’s why it’s the correct choice:

It’s an air barrier.

The foam expands into every gap, seam, and irregular corner, then cures solid. The leak is gone.

It’s a vapor retarder.

At two inches or more, closed-cell foam blocks moisture from reaching the cold framing, so condensation never forms.

High R-value per inch.

Roughly R-6.5 to R-7 per inch — the highest of any commonly installed insulation, which matters in a shallow cavity where you don’t have much depth to work with.

It adds structural rigidity

and won’t sag, settle, or absorb water over time.

Most Southern Wisconsin homes get two to three inches at the rim, depending on framing depth and the target R-value. We’ll confirm the right thickness during the walkthrough.

Focus on Energy Rebates

Wisconsin’s Focus on Energy program offers rebates on insulation and air sealing work, and rim joist sealing is often part of a qualifying package. A few things worth knowing:

We’re happy to walk you through the current program during your estimate.

What your neighbors are saying

    
 
 
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   Ariel Vargas 
 
 
 
 Trustindex verifies that the original source of the review is Google. 10/10 all across the board! Lydia is an absolute pleasure to work with. Such a ray of sunshine😝🌞 Great service, just great great great !
  
 
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   Rod Marquette 
 
 
 
 Trustindex verifies that the original source of the review is Google. Erik was very knowledgeable. The sales process was painless.  I noticed a difference in my home.
  
 
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   Shawn Flyte 
 
 
 
 Trustindex verifies that the original source of the review is Google. The Cozy Walls team was an absolute pleasure to work with. I have an older home that was originally built in the early 1900’s. It was drafty and I could hear a lot of road noise from inside my living room. That is until Cozy Walls did their thing. The noise reduction was the first thing I noticed. I couldn’t believe the difference. Erik was very informative and the Veteran Discount helped a lot! Definitely worth the cost as I’m already noticing a difference in my energy bill. Highly recommend!
  
 
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   Cade Walters 
 
 
 
 Trustindex verifies that the original source of the review is Google. This Company’s Great, Employees are very nice and hardworking. Would recommend to anyone looking to get their walls insulated!
  
 
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   Samuel Williams 
 
 
 
 Trustindex verifies that the original source of the review is Google. Took 3 times the quote to finish. Left unfixed exterior wall damage. I had to find someone else to fix.
  
 
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   Austin Brown 
 
 
 
 Trustindex verifies that the original source of the review is Google. Me and my wife just bought our first house and discovered that our bedroom was very cold compared to the rest of the house, and that our furnace was almost constantly running struggling to keep the house warm. Cozy Walls came out and insulated the entire house and garage and found out that most of our walls had no insulation anymore due to the age and the insulation deteriorating. Since having work done our bedroom is much warmer and our furnace runs a lot less, saving us money! Amy and Zach run a great business and their crew was very professional. And it was very affordable and cost-effective. They placed blankets over my motorcycles in the garage so they wouldn't get dirty during the work being performed and they cleaned up everything very well after. Cannot recommend Cozy Walls enough if you need any insulation done in your house
  
 
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   Dawn Coker 
 
 
 
 Trustindex verifies that the original source of the review is Google. WELL worth the read! Customer service ?  This company is right on point! From Zack and Amy to the rest of their team, wow! Until I found these two companies, I had an awful and long time getting one to return my calls or come out for an estimate. I saw an ad on TV for Healthy Home Insulation, left a message on a Sunday, they came out the next day! Before Erik left he gave me an estimate for attic and basement (Healthy Homes) as well the walls from (Cozy Walls Insulation.) They were out here the following week to complete the job! I have HORRIBLE allergies that can cause my eyes to swell shut to causing vertigo. I was concerned that the smell of foam spray would be an issue. Amy, Cozy Walls said they would come out try a wall see how it went. If it was ok, complete the job, if not, we would figure something out. To me this is a company that truly cares about their customers! BOTH companies have gone above and beyond from start to finish. I would recommend them to anyone!
  
 
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   Lila Balboa 
 
 
 
 Trustindex verifies that the original source of the review is Google. They give an Awesome customer experience Very knowledgeable and explain the whole process!
  
 
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   Chad Nickelson 
 
 
 
 Trustindex verifies that the original source of the review is Google. Great honest company highly recommend if youre looking to update the insulation in your home!
  
 
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   Mike Jacobs 
 
 
 
 Trustindex verifies that the original source of the review is Google. This is a great company to do business with!
  
 
  
  
 
 
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What homeowners here ask

How much does rim joist insulation cost?

Pricing depends on linear footage, framing depth, and how much prep is involved. Most homes fall in a predictable range, and we give you a firm written number after the walkthrough — no ballpark that changes later.

Do I have to leave the house while you spray?

We recommend that occupants stay out of the immediate work area during application and for a few hours afterward. We’ll give you a specific timeline for your job.

Can I do this myself with the kits from the hardware store?

The two-part kits work for small patches, but they’re difficult to apply evenly, expensive per board foot at scale, and easy to get wrong on thickness. For a full perimeter, professional equipment gets you consistent coverage and consistent R-value.

What if there’s already rot in my rim joist?

We’ll flag it during the walkthrough. Foam over rotted framing just hides a problem. If we find structural damage, we’ll tell you before we quote the work.

Does this help in the summer too?

Yes. The same air leak that lets cold in during winter lets humid air in during summer, which loads up your air conditioner and raises basement humidity.